Process and apparatus for recording hysteresis curves of magnetic materials

Abstract

A process for measuring the hysteresis curve of magnetic materials comprises the generation of a magnetic field of varying amplitude, placing the sample to be measured into that field with a measuring coil and a potential coil attached thereto, integrating the signals from those coils to provide simultaneous values of flux density B and internal field intensity H, recording and storing the B and H values and converting these values to digital units in a transient recorder in real time and then feeding these signals to an X-Y recorder, a printer or other display device at a slower rate of speed to provide a hysteresis curve, or a display of programmed values of magnetic characteristics of the sample being measured.

What is claimed is: 
     
       1. Process for measuring the hysteresis curve of a magnetic material comprising the steps of: subjecting a magnetic material for a period of time to an alternating magnetic field of decreasing amplitude generated by periodic discharge of a capacitor connected with a field coil;   measuring the flux density B to which said magnetic material is subjected and the internal field intensity H of said material during said period of time;   converting the values of B and H into digital units and recording said digital units of B and H separately and simultaneously in real time, and;   retrieving from said stored units in the form of electrical signals at least one value of units for each of both B and H which were stored at a given instant in time.   
     
     
       2. Process of claim 1, wherein said electrical signals for one instant of time are fed to a digital display to display a specific characteristic of the measured material, such as remanence B r  or coercive field intensity H C . 
     
     
       3. Process of claim 1, wherein a succession of said signals are fed to an analog display device, such as an X-Y recorder to provide at least a portion of a hysteresis curve of the measured material. 
     
     
       4. Process of claim 1, wherein a succession of said signals are fed to a digital display device, such as a printer. 
     
     
       5. Process of any one of claims 1, 2 or 3, wherein the material being measured is a soft magnetic material. 
     
     
       6. Process of claim 5, which includes the step of subjecting the material to be measured to an alternating magnetic field having an adjustable curve shape and frequency. 
     
     
       7. Process of any one of claims 1, 2 or 3, wherein the material being measured is a hard magnetic material. 
     
     
       8. Process of any one of claims 1, 2 or 3, which includes the steps of subjecting the material to be measured to a magnetic field having a first polarity and an amplitude sufficient to saturate said material and a second amplitude of reversed polarity greater than the coercive field intensity  J  H C  of the measured material. 
     
     
       9. Process of any one of claims 1, 2 or 3 which includes the step of subjecting the material to be measured to an alternating magnetic field having a frequency insufficient to create eddy current that could distort measurements. 
     
     
       10. Process of any one of claims 1, 2 or 3, wherein electrical values of said flux density B and internal field intensity H are obtained by means of sensing instruments mounted on the material to be measured. 
     
     
       11. Apparatus for measuring the hysteresis curve of a magnetic material, comprising: means to generate an alternating magnetic field of short duration having a high initial amplitude with a decreasing amplitude thereafter within which field a sample to be measured may be placed;   measuring coil means and potential coil means, both to be attached to said sample;   integrating means connected with said measuring coil means and potential coil means for converting electrical values detected by said coils into respective electrical signals indicating values of flux density B and internal field intensity H of said sample while in said magnetic field;   transient recorder means having at least two channels connected to said integrating means for recording and storing said values of B and H in real time, and for converting said values into digital units; and   display means connected to the output of said transient recorder means for displaying at least one set of simultaneous values of B and H.   
     
     
       12. Apparatus defined in claim 11, wherein said display means is an X-Y recorder for recording at a lower speed at least a portion of the hysteresis curve of said sample. 
     
     
       13. Apparatus defined in claim 11, wherein said display means is a printer for recording simultaneous values of B and H, or programmed characteristics of said sample derived from said values of B and H.